Double Signatures

I work at a company that places two signatures on the bottom of thank you letters.Their common practice is to print the organization name under "sincerely" and then place both the Manager's signature and the Board President's signature with their underneath the organization's name.

This cannot be the correct way of doing this. I do not believe it is necessary to re-listed the company name under both these signatures since it is at the top of the letterhead.

What is the correct form?

[Ouisch]

You are correct. If the letter is written on company letterhead, it is considered incorrect form to repeat the company's name in the signature. (A lot of executives/assistants make his mistake, however.)

[Charlie Bernstein]

But it's fine to put people's job titles under their names.